The present invention relates to a turbo pump of which a pump impeller is rotated by rotation of a turbine wheel, and in particular to a turbo pump in which fluid comprising liquid, gas, or an intermediate such as a two-phase fluid mixture of liquid and gas can be employed as working fluid of a turbine wheel and in which fluid comprising liquid, gas, or an intermediate such as a two-phase fluid mixture of liquid and gas can be employed as carried fluid of a pump impeller just like the working fluid of the turbine wheel.
Furthermore, the present invention relates to a fluid supply system using a turbo pump which intensively performs a supply management by pumping out liquid to store it in a tank, wherein the turbo pump disposed in liquid stored in a liquid-storing place such as a deep well or the like, sending out the liquid from the tank to a supply line.
Conventionally, a turbocharger which is designed to use gas as fluid is well known as a turbo pump. Such turbochargers have been developed with development of turbojet engines of aircraft. Today, many of them are each used as a turbocharger for fuel fluid supply system of a vehicle.
A turbocharger disclosed in Japanese Utility model Gazette No. H4(1992)-15956 is a typical type of turbocharger according to the conventional design. As shown in FIG. 15, the turbocharger 70 comprises a compressor impeller 72 rotatably disposed in a compressor casing 71 and a turbine wheel 75 fixed to a rotor shaft 73 of the compressor impeller 72 and rotatably disposed in a turbine housing 74. The turbine wheel 75 is rotated by exhaust gas of an engine (not shown) which is introduced from a scroll portion 76 and then the compressor impeller 72 is rotated by the rotation of the turbine wheel 75 through the rotor shaft 73. By the rotation of the compressor impeller 72, air is sucked from an inlet 77 of the compressor casing 71 and is sent toward the engine through a scroll portion 78 of the compressor casing 71. The exhaust gas of the engine is exhausted from an outlet 79 of the turbine housing 74 after rotating the turbine wheel 75.
Thereby, it is possible to increase the output of the engine and to make the speed of the engine higher.
By the way, in the turbo pump, generally such as the turbocharger or the like, unless making the speed higher, it is impossible to improve the efficiency of the system. Thereby there is no sense in providing the turbo pump to the system. In the conventional turbo pump, such as the turbocharger described above, the high speed phenomenon that occurs when the fluid used is a gas, causes no particular trouble. Therefore, when the fluid used is gas, it is relatively easy to make the speed of the turbo pump higher so that various turbo pumps has been developed in the past.
In recent years, there is a large demand for carrying liquid or an intermediate comprising a two-phase fluid mixture of liquid and gas. Therefore, a turbo pump which can carry liquid or an intermediate is necessary.
However, as unlikely as it is to occur when gas is employed as the fluid for the turbo pump, when liquid is employed as the fluid, cavitation, which is a phenomenon peculiar to liquid, easily occurs as the turbo pump is speeded up. In the turbo pump in which liquid is employed, it is not easy to make the speeds of the turbine and the pump higher due to cavitation.
Published Unexamined Patent Application No. S51(1976)-91003 proposed a deep-well pump, as the turbo pump in which liquid is employed as the working fluid for turbine, which is designed for pumping out high-temperature brine of which temperature is between 177.degree. C. and 331.degree. C. from a geothermal well of which depth is 1,500.about.3,000 m below the ground.
Since the deep-well pump is used for a special purpose of pumping up the high-temperature brine from the place where is quite deep, 1,500.about.3,000 m below the ground, a turbine of the deep-well pump has a staged structure to increase an output of a pump thereof.
However, by making the turbine staged structure as mentioned above, it makes the structure complex and makes the system large, further, makes the cost high. In addition, because of this situation, it is difficult to set the revolution of the pump at a high speed. Even if the revolution is set at somewhat high speed, the cavitation which is a phenomenon peculiar to liquid occurs.
Consequently, an ordinary turbo pump in which liquid or an intermediate is employed and which has a simple structure and is low-priced is not practically used yet for the time being.
On the other hand, a fluid supply system is shown in FIG. 16 as a fluid supply system in which a liquid pump disposed in liquid is used. In this Figure, the numeral 50 designates the fluid supply system, the numeral 51 designates a deep well, the numeral 52 designates a staged pump, the numeral 53 designates an electric motor, the numeral 54 designates a lifting pipe, the numeral 55 designates a check valve, the numeral 56 designates a sluice valve, the numeral 57 designates a pressure tank, the numeral 58 designates a pipeline to a supply line, the numeral 59 designates a pressure switch, the numeral 60 designates a control board, the numeral 61 designates a cable for connecting the pressure switch 59 and the control board 60 together, the numeral 62 designates a cable for connecting the electric motor 53 and the control board 60 together, the numeral 63 designates a head tank, the numeral 64 designates a pipeline to the supply line, the numeral 65 designates a water level gage, and the numeral 66 designates a cable for connecting the water level gage 65 and the control board 60.
As shown in FIG. 16, in the fluid supply system 50, the staged pump 2 is disposed under the water in the deep well 51, and the staged pump 52 is designed to be a submersible motor pump which is driven by the electric motor 53. Water sucked by the staged pump 52 is carried to the pressure tank 57 through the lifting pipe 54 and stored in the pressure tank 57. The water stored in the pressure tank 57 is carried to the supply line through the pipeline 58 and is supplied from each supplying portion of the supply line. In this case, the inner pressure of the pressure tank 57 is maintained at a predetermined level, and the submersible staged pump is operated by the pressure. As the water in the pressure tank 57 is decreased by supplying the water into the supply line, the inner pressure of the pressure tank 57 is reduced. When the inner pressure of the pressure tank 57 is reduced below the predetermined level, the pressure switch 59 detects this condition, then operates to output a pressure reducing detecting signal to the control board 60. The control board 60 received this signal outputs a driving signal to the electric motor 53 through the cable 62 so the electric motor 53 and the staged pump 52 are driven. Thereby, the staged pump 52 sucks water in the deep well 51 to carry and store the water into the pressure tank 57 through the lifting pipe 54. As the water is carried into the pressure tank 57, the inner pressure of the pressure tank 57 is increased. As the, inner pressure of the pressure tank 57 is increased to the predetermined level, the pressure switch 59 does not output the pressure reducing detecting signal into the control board 60 any more and the control board 60 then stops the operations of the electric motor 53 and the staged pump 52. Therefore, the water is stopped supplying into the pressure tank 57 so that the inner pressure of the pressure tank 57 can be maintained at the predetermined level. Thus, the intensive supply management which supplies water to a plurality of supplying portions from the one deep well 51 is performed.
Instead of the pressure tank 57, the head tank 63 may be disposed at a position higher than the supply line to store water at a predetermined water level in the head tank 63 through the lifting pipe 54 and then supply the water to the supply line from the head tank 63 through the pipeline 64. In this case, the staged pump is controlled by the control board 60 according to a water level decreasing signal by the water level gage 65 disposed in the head tank 63.
However, in the fluid supply system 50 in which the conventional submersible motor pump is employed, the electric motor 53 of the staged pump 52 and a portion of the cable 62 for supplying the driving control signal from the control board 60 to the staged pump 52 are disposed in the water. Therefore, it is necessary to securely waterproof the electric motor 53, the cable 62, and the connecting portion between the cable 62 and the electric motor 53. Further, since the staged pump 52 is relatively large, it is troublesome and not easy to dispose the staged pump 52 into the water in the long and narrow deep well 51, thereby not only taking many man-hours to install it but also making the maintenance quite troublesome. Furthermore, since it is necessary to make the electric motor 53 and the cable 62 to waterproof structure, it costs a great deal.
In addition, with blades of an impeller of such a conventional staged pump, as the impeller is speeded up during operation of the pump, cavitation occurs so that the revolution of the impeller can not be high.